To observe minute shapes on the surface of a sample, scanning tunneling microscopes (STM) have been used widely. Some of such conventional scanning tunneling microscopes include one that applies alternating current voltage as well as direct current voltage between a probe and a sample to generate a current, extracts an alternating current component from the generated current, and measures the frequency characteristics of a conductance component and a susceptance component of admittance between the probe and the sample from the extracted alternating current component, thereby analyzing the kind and composition of a material on the surface of the sample (cf., PTL 1).
A method known in the art includes locally irradiating intensity-modulated laser light with a predetermined frequency onto the surface of a sample to generate micro displacement based on a photo-acoustic effect and observing the micro displacement with a scanning tunneling microscope for obtaining information about the surface or inside of the sample (cf., PTL 2).